1. Field of the Invention
This invention relates to photo diodes, and more particularly, to a photo diode that can polarize incident light before the light is sensed by the light-sensitive areas so that the photo diode is capable of detecting the intensity of the component of the incident light that is polarized in a specific direction.
2. Description of Related Art
Two conventional photo diodes are respectively depicted in the following with reference to FIGS. 1 and 2.
As shown in FIG. 1, the first conventional photo diode is constructed on a P-type semiconductor substrate (p-sub) 100. Through various semiconductor fabrication processes, the substrate 100 is formed with a plurality of field oxide (FOX) regions 101, a gate electrode 102, an n.sup.+ source/drain region 103, an n.sup.+ light-sensitive area 104, and a pair of n.sup.- lightly-doped area 105.
As shown in FIG. 2, the second conventional photo diode is constructed on an N-type semiconductor substrate (n-sub) 200. Through various semiconductor fabrication processes, the substrate 200 is formed with a plurality of FOX regions 201, a p.sup.+ light-sensitive area 202, and a pair of n.sup.+ doped areas 203.
Both of the foregoing two types of photo diodes can be further formed with a color filter structure (not shown) over the respective light-sensitive area (i.e., the n.sup.+ light-sensitive area 104 in FIG. 1 and the p.sup.+ light-sensitive area 202 in FIG. 2) so as to separate the incident light into red, green, and blue (RGB) components for color detection when used in color image sensors.
One common drawback to the foregoing two types of photo diodes, however, is that they unable to polarize the incident light before it is sensed by the light-sensitive areas so that they are incapable of detecting the intensity of the light polarized in a specific direction.